Caption: Hydrocephalus. Coloured computed tomography (CT) scan of the brain of a 22 year old patient with hydrocephalus (fluid in the brain). This is a condition in which there is an accumulation of cerebrospinal fluid (CSF), the liquid that surrounds and cushions the brain. This leads to dilation of the ventricles (yellow), the cavities in the brain that circulate CSF, and the compression of the brain tissue. Treatment is with drainage of the fluid.